Signaling system



Oct. 23, 1928. 1,688,997

C A. SPRAGUE SIGNALING SYSTEM Filed July 2o, 192:5

\ Q /n Ven/0f.

C70/en c e A. Sprague.

by A//y Patented' Oct. 23, 1928.

UNITED STATES PATENT OFFICE.

CLARENCE A. SPRAGUE, 0F EAST ORANGE, JERSEY, ASSIGNOR T0 WESTERN ELEC- TRIO COMPANY, INCORPORATED-, 0F NEW YORK, N. Y., A. CORPORATION 0F NEW YORK.

SIGNALING SYSTEM.

Application filed July 20,

The invention relates to a signaling system and more particularly to a system of signaling by means of modulated energy waves in which the signal to be transmitted is preferably impressed upon a more or less regular wave known as `a carrier and the combined Waves at the receiving end are demodulated or disassociated in order to venable the signal to be effective.

Systems of this general character in which low frequency waves are used to modulate, high` frequency electrical waves are in common use. It has also been -proposed to transmit compressional wave signals through a fluid medium such as water for the purpose of submarine signaling. 'In systems of this sort, however, the signal-is impressed upon a larve body of fluid 'and radiates in all directions from the transmitting point. Signals transmitted in this way, of. course, can be picked vup by any one havingthe proper apparatus working in the medium" through which the signals are transmitted. In this respect the usual submarine signaling system is analogous to radio broadcasting systems. It is, also, common to transmit modulated waves -of energy over wires or solid conductors of electricity, this method having well known advantages.

In accordance with the present invention, however, the carrier waves are generated and transmitted through a confined. fluid in the form of impulsesv in the fluid. The fluid is conveniently confined in a tubular conduit or pipe which is connected to transmitting and receiving stations. The waves may be impressed upon the fluid within the pipe by electrically actuated means, thus permitting the transfer of modulated waves directly to the fluid, the modulation or combination of the signaling and carrier wave being accomplished electrically by means of well known apparatus for the purpose. A. feature of the invention, therefore, refers to a method and apparatus for transmitting wave energy modulatedlto form a signal through a confined fluid medium.

Related features have to do with the apparatus for impressing the wave energy on the medium and for detecting and receiving from said medium the .effect of this wave energy. f

These and other features of the invention will more clearly appear in the speci- 1923. Serial No. 652,692.

tion of a two-way or duplex system and Fig.

2 shows in detail a sectional view of such apparatus taken on the line II-II of Fig. 1.

Referring now to the drawings, a conduit or pipe is shown at 1 which may be made of metal or other suitable material and which as shown is provided with an interior lining 2 of some material, such as lead, which does not readily transmit wave energy. The purpose of the lining is to prevent radiation or dispersion through the walls of the pipe of the energy passing along the pipe. A similar effect may be obtained by using relatively heavy exterior walls. Associated with the pipe 1 through of this pump is to raise the pressure of theA fluid in the pipe to a desired value, after which the valve 3 may be closed. This pump may serve also to pump a constant stream of fluid through the pipe, it not being essential for the operation of the signaling system as will hereafter appear that the fluid be quiescent. For this reason advantage may be taken of existing pipe lines used for pumping fluids such as oil.`

The pipe 1 terminates at the sending and receiving stations in an enlarged bulb or chamber 5 which tapers off' into a compensating pipe 6. A partition or septum formed by the diaphragm 7 and the parallel diapliragms 8 with their supporting frame 9 divides the main pipe 1 from the compensating pipe or tube 6. -I/lflieffidiaphragms 8 are utilized to impress theenergy of the signals upon the fluid and the diaphragm 7 is utilized to receive such signals. In order that the diaphragm 7 may not be -affected by the vibrations of the diaphragms 8 at the transmitting station the characteristics chosen to balance those of the .tube 1. The

compensating tube 6, therefore, forms the equivalent of the artificial line used in systems of electro-communication and performs the same function. the pipe 1 maybe simulated by the smaller compensating tube 6 by giving the latter a much smaller diameter and a taper at the end adjacent the sound generator, -as shown,

The characteristics 'of by using various thicknesses of tube wall to vary the elasticity thereof, by using various linings of different materials, by using a fluid of suitable characteristics filling the tube 6, by perforating the walls of tube 6 at intervals, by surrounding the Walls with different absorbing material such as a layer of sand, or by any combination of these means.

The principal factor to be compensated for is probably the mechanical resistance offered by the pipe 1 to wave motion. The elasticity of the tube would have some effect as would its diameter and ge-neral configuration. Regardless of the factors which enter into the problem the compensating tube, with a due regard for such factors, may be constructed by experiment, or may be made adjustable, the main requirement being that the diaphragm 7` be equally and oppositely affected by the diaphragms 8.

There may be, as shownv in the sectional view of Fig. 2, a number of diaphragms all of which may be similarly actuated to impress waves of different carrier frequency upon the fluid without interference or without interfering with the receiving diaphragm 7.

The diaphragms 8 may be actuated through any suitable mechanical or electrical oscillator, there being here chosen for purposes of illustration an electrically controlled device which is well known in the electro-communication lart and in the art of submarine sound signaling as the Fessenden oscillator. It is disclosed in Fessenden Patent No. 1,213,610 of January 23, 1917. In general it consists of a magnetic structure 10 in which is embedded a magnetizing coil 11 connected with a suitable source of current. The magnetic structure and coil are toroidal in form and positioned in the opening ofthe toroid is a copper sleeve 12, which as shown is connected through a link 13 to a diaphragm 14, secured to and closing an opening of an air chamber included between the diaphragms 8. Within the copper ,f sleeve is a magnetizing coil 15 which when energized through 'variable electrical currents. causes a corresponding vibration of the diaphragm 14. Vibration of the diaphragm 14, by means of the fluid confined between that diaphragm and the diaphragms 8 is communicated to the corresponding pair of diaphragms 8. The diaphragm 7 carries a microphone detector 16 which may be any one of several well known types. The inertia type microphone usedextensively for the detection of submarine noises will be suitable for ,the purpose.

There is foreach station a single microphone or receiving device 16 and a plurality of oscillatorsof the Fessenden type. This apparatus is duplicated at each station of which there may be as many as may b e desired along the length of the tube or pipe. A Variety of electrical apparatus may be used for the purpose of impressing the signals on the transmitting mechanism of the invention, that illustrated herein being typical. As shown there are low frequency signal lines 17 and 18 which may be the ordinary telephone lines with which are used the usual telephonie apparatus. There may be as many of these lines as there are oscillators per station or in other words as many as Athere are channels of communication through the fluid medium. The line 17 is associated with the signal transmission ap- -paratus by lmeans of the hybrid coil 19 and its associated balancing network 20. A similar hybrid coil 21 and balancing network 22 is shown for associating the line 18 lwith the transmitting and receiving apparatus.

There is indicated diagrammatically by the rectangle A-l, M-1, A-2 and F-l, an amplifier, a modulator, a second amplifier and a filter. Also associated with the amplifier and modulator is indicated a source of oscillations O-1, which ordinarily would be of a frequency too high for the unaided ear to detect. Frequencies in the range from 5.0007t-o 20,000 are suitable although higher frequencies may be used for relatively short distance operation. The amplifiers may be of any standard type preferably of the thermionic vacuum tube variety; similarly the oscillator and modulator may be of an well known type although it is preferre to use a vacuum tube oscillator and a Vacuum tube modulating arrangement.'

Similarly the filter F-l which is designed to pass (through the transmitting apparatus) only a certain band of frequencies produced dby the modulated output of the oscillator O-1, may be the usual Campbell filter.

All of this apparatus is well known and is shown and described in issued patents and in` treatises on radio signaling, so that no detailed descriptionv need here be given.

The rectangles A-3, D-2 and F--2 indicate an amplifier, detector and filter respectively. This apparatus may be similar to amplifiers and filters above described and the detector may be the usual vacuum tube detector or demodulator as it is sometimes called.

Associated with the line 18 is apparatus similar to that associated with the line. 17, comprising the hybrid coil 21, amplifier A-4, oscillator 0 2, modulator M-3, amplifier A-, filter F-3, amplifier A-6, detector D-f and filter F-4. The oscillator O-2 lwill be arranged to produce a frequency different from that produced by the oscillator O-l and the filters F-3 and F-f-f: will be constructed to pass different bands of frequencies which are different also than` those passed by filters F-1 and F-2 respectively. Each of the filters F--l and a maximum number of channels in the ava-ilable frequency range.

The shape of the connection of the pipe from pump 4 to pipe 1 should be such as to minimize reflections whenever those adjuncts are used. The frequency introduced by the pump mechanism is preferably outside the voice range. This disturbance may be' reduced by means of a balancing pipe 23 supplying pressure to the tube 6 through openings 24,. 24, the length of pipe 23 and diameter of openings 24 being suchv that the effects upon the two sides of diaphragm 7 are equal and opposite.

With the understanding that the apparatus both electrical and mechanical is duplicated at each station, the operation of the system will now be described, assuming that there are two stations one located at either end of the pipe, that this pipe is filled with a suitable fluid which is maintained at a con. stant pressure and that the fluid in the pipe 6 is at the same pressure. It will. also be assumed that-a telephone subscriber using a line such as 17 at the transmitting station desires to converse with a subscriber who may be connected with a line similar to line 17 at the receiving station. Voice currents coming in over the line 17 will, because of the balanced windings of the hybrid coil`19, have no effect onl the apparatus D-2 and F-2 of the receiving channel. They will,

however, be transmitted through the series windings of the coil to the input of the vacuum tube amplifier A-l and there amplified.V Carrier waves of a definite frequency which will differ for each channel of communication it is desired to establish are impressed on the input of the modulator M-l together with the amplified voice currents from the amplifier A-l. The modulated carrier waves are thenamplified by the amplifier A-2 and pass through the filter F-l to the energizing coil 15 of the mechanical oscillator. Corresponding modulated waves will be impressed upon the fluid in the tube 1 and in the compensating tube 6 through the diaphragms 8. These modulated waves will be transmitted through the tube 1 to the distant station. They will be without effect on the diaphragm 7 and the receiving apparatus associated therewith because of the compensating effect of the tube 6. At the receiving stations this balance will not exist'since the received waves will be impressed upon one side only of the diaphragm 7. This diaphragm will respond not merely to carrier waves of a single frequency but to all `carrier waves that are being transmitted at any time through the tube 1. The diaphragm 7 will in a well known manner cause resistance variations in the .electrical circuit corresponding to the waves which set it into vibration and this vibration will be va faithful copy of the electrical variations impressed on the fluid medium at the transmitting station. These variations pass through the filter F-2 as in the case assumed the particular signals transmitted are of the carrier frequency passed by the filter F-2 and not by the filter F 4, and are impressed upon the input of the detector D-2 where they are demodulated. The demodulated waves are amplified by the amplifier A-3 and in the form of voice currents are impressed upon the line corresponding tothe line 17 at the receiving station.

It is not thought necessary to enter into a detailed description of the operation of the electrical apparatus at the stations since this is to all intents and purposes the same as that used in well known multiplex systems of signaling by means of modulated carriei waves over electrical conductors, While the system has been disclosed in connection with an arrangement for transmitting speech, it. is within the scope of the invention, of course, to transmit speech or other signals such as telegraphic signals without the aid of carrier currents and also to transm yt carrier currents modulated in accordance with telegraphic signals. The carrier frequencies may lie in the range from 10 cycles per second upward. Also as will be apparent certain features of the invention are applicable to simplex systems. Also the invention in a broad aspect fs independent of the particular fluid usedand of the pressure maintained although the pressure is preferably maintained substantially constant and usually will be maintained at a reasonably high point, especially when the fluid used is a gas rather than a liquid.

The invention has been described as applied to a signaling system of quite general application. A number of specific uses of the invention, however, may be mentioned among whichis as a substitute for present forms of electrical submarine cable systems for operation over relatively short distances as between islands or the mainland and an island. The cost of a signaling, pipe line of this nature approximates that of an electric cable and in addition to carrying the same or greater amount of signaling traffic may serve as a. pipeline for oil or other fluid. In ycase of submarine operation the pipe 1 may be filled with sea water if not used as a pipe line. In this case openings may exist in the walls ofthe pipe without materially affecting the operation of the system. In fact small openingsmay be made at intervals to serve a function somewhat analogous to the resistance leakage paths employed in electric from the ends toward the center, where large pressures are employed at the two ends as for duplex operation or where a pump is used at each end. When the cable is employed in deep water of course the hydrostatic pressure within the pipe increases with the depth the same as the pressure without the pipe so that there is no tendency to rupture on account of depth if theliqud within the pipe is substantially of the same density as that without. Likewise, the thickness of the lining material may be progressively less from the ends toward the center of the cable.

When the cable 'is constructed as a combined pipe line and compressional wave signaling cable`and a relatively large constant pressure is impressed by the end only of the cable or conduit, the thickness of the walls of the conduit should be made progressively less from that end to the other end. That is, the thickness should, ideally, vary in proportion as the resultant pressure due bothto the operation of the pump or pumps and the operation of the transmitter or transmitters. The examples given in this and the above paragraph c onform with this ideal although mentioning specifically, in each reference, only certain of these four possiblev means .for producing pressure. Incase high eliiciency of operation is desired it is preferable to transmit the acoustic waves at high pressure and low am-- plitude.

Another use of the invention which may be mentioned is in connection with the water systems of cities and vvillages wherein itis particularly applicable for broadcasting news and entertainment through the pipes and conduits of such system. In an arrangement of this sort a single one-way channel may be employed and reception may be accomplished by ordinary radio receiving apparatus such as is employed for rece1ving electromagnetic Waves from radio broadcasting stations.

Other suggested applications o f the invention are to air, gas or water pipes of any structure such as a mine, manufacturing plant.I ship or train-of cars.

What is claimed is:

v1. An electro-compressional signaling sys* tem comprising a conduit or pipe filled with a fiuid and extending between two distant points, means at each of said points for simultaneously impressing upon the fluid in pump at yone said pipe high frequency compressional.`

pipe a plurality of high frequency waves modulated `in accordance with. signals, means at each of said point-s for simultaneously receiving said modulated waves from the distant point and obtaining Vthe signals therefrom, and means at each of said points for substantially preventing the local transmitting apparatus from interfering with the y operation of the receivin apparatus.

3. Means for transmitting compressional wave energy comprising a pipe or, conduit, liquid filling said pipe, the mass of said pipe per unit length being large relative to that of the corresponding contained liquid, means for generating high frequency oscillations modulated in accordance with a signal, and vibratable means for impressing said oscillations upon said Huid.

4. Means for signaling from one place to another between which is a body of water, said means comprising a heavy walled pipe or conduit immersed in said body of water,

water filling said pipe, means for generating .compressional signaling waves in said water in said pipe and means at a point distant 'therefrom for receiving said signaling waves.

5. Means for signaling -from one place to another between which is abody of water,

said means comprising a heavy walled pipe or conduit immersed in said body of Water, liquid filling said pipe, means for generating electrical signaling waves, means for transforming said electrical waves to compressional .waves in said liquid in` said pipe, and means at a distant point for receiving said compressional waves and transforming them to electrical waves.

6. Means for transmitting compressional signaling waves comprisinga heavy walled pipe or conduit filled with a liquid and a lining for said pipe composed of material which minimizes transfer of compressional wave energy from said liquid to the. walls of said pipe.

7. An electro-.compressional signaling system comprising a pipe or conduit filled with fluid, a second pipe or conduit having transmission characteristics similar to the' rst and filled with fluid, vibratable means for simultaneously impressing compressional signaling waves upon the fluid in each vof said pipes and an acoustical receiving instrument associated with the fluid in both said pipes and balanced with respect to the waves set up by said vibratable means.

8. An electro-compressional duplex` signaling system comprisingaV pipe or conduit filled with fluid, a second pipe or conduit filled With fluid andhaving the same transmission characteristics as said first mentioned pipe, means for simultaneously impressing compressional waves upon the fluid in each of said pipes, and vibratable means upon which said waves in said pipes act equally and oppositely so as to produce subtantially no effect thereon.

9. A combined system -for transmitting a liquid and for signaling comprising two similar pipes or conduits having similar characteristics, a pump for transmitting fluid through one of said pipes, a body of fluid in said second pipe, means for simultaneously impressing compressional signaling waves upon the fiuid in both said pipes, vibratable means upon which said signaling waves act equally and oppositely, and means for varying the pressure of the fluid in said second.pipe in phase with the variations produced in the fiuid in said first pipe by said pump to nullify the effect of the latter variations upon said vibratable means.

10. An electro-compressional wave signaling system comprising a pipe or conduit filled with fluid, a second pipe or conduit of similar characteristics filled with fluid, a diaphragm in the wall of each of said conduits, a chamber enclosed in part by said diaphragms, a fluid filling said chamber, a plurality of vibratable elements in Contact with said fluid, and means for vibrating each of said vibratable means at a different constant rate.

11. Means for signaling between remote points comprising a pipe extending between said points, liquid filling said pipe, means at one of said points for setting up powerful Waves in said liquid and means at the other of said points for receiving said waves and obtaining a signal indication therefrom, said pipe having thick walls where said waves are generated in said pipe and progressively thinner walls from there to a point of minimum wave energy in said pipe.

12. Means for transmitting compressional waves comprising awave guiding pipe containing a fluid medium, and a lining therefor of material which transmits said waves less readily than the material of said pipe.

13. A compressional wave transmission system comprising a conduit containing a fluid, a second conduit also containing a fluid, means for simultaneously impressing compressional Waves upon the fluid in each of said conduits, anda compressional wave responsive means, said responsive means being tending between distant points, a liquid in said pipe, means for impressing high frequency waves modulated in accordaime with speech upon the liquid in the pipe ai; one point, vibratable means associated with the liquid in said pipe at a distant point, electrical means operated by said vibratable means, and a high frequency wave detector operated by said electrical means for obtaining low frequency speech waves from said high frequency modulated waves.

15. In a compressional signaling system comprising a pipe or conduit extending between distant points, a liquid in said pipe, means for impressing high frequency compressional waves modulated in accordance with signals upon the liquid in the pipe at one point, vibratable means associated with the liquid in said pipe at a distant point for converting said compressional waves into mechanical motion, and a high frequency wave detector operated responsively to the operation of said vibratable means for'obtaining low frequency signal waves from said high frequency modulatedwaves.

16. The combination recited in claim 15, including additionally a means for progressively translating the liquid as a whole in said pipe during the signaling operation.

17. Means for signaling from one place to another between which is a body of liquid, said means comprising a heavy walled pipe oi conduit immersed 'in said body of liquid, a liquid of the same kind asthat constituting said body filling said pipe, means for generating compressional signaling waves in said liquid in said pipe, and means at a point distant therefrom for receiving said signaling waves. i

- 18. In combination, a liquid, a pipe immersed in said liquid, a liquid of the same kind as said first mentioned liquid filling said pipe, said pipe having openings through its walls at longitudinally spaced intervals. and means for signaling by compressional waves through the liquid in said pipe.

19. The combination specified in claim 18, in which the openings are of progressively greater area in a direction from a transmitting terminal toward the center.

In Witness whereof, I hereunto subscribe my name this 17 th day of July A. D.,

CLARENCE A. SPRAGUE. 

